Foundation Type for Passive House on Rocky Site
Hi, I’m considering a PassivHaus standard project up in northern Ontario.
For the foundation, I’ve looked into Frost Protected Shallow Foundation (FPSF), as well as helical piers, and the traditional full basement dig. I’m leaning toward piers just because there’s less heavy machine work involved and I like the idea of being nearly completely separated from ground freeze issues. Initial thought is to leave the area below the house open, so there are no complicated crawl space issues to deal with.
However, there are large rock formations in the area (Sudbury Basin) and it crossed my mind that if one could find a fairly smooth, large rock formation and add just enough concrete and fill to create a perfectly smooth surface, they’d be on very solid ground with no concern for frost heave. I never see this, and I have a suspicion that it is a stupid idea, but I’m not exactly sure what’s wrong with it. Anyone care to comment? Another version would be to use piers drilled into the rock which would require no fill / concrete leveling but might be more costly than the concrete option.
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